Printing plate clamping device

ABSTRACT

A printing plate clamping device, particularly for web-fed rotary offset printing presses, which comprises a plate cylinder having a longitudinal groove and including end walls. A clamping shaft is disposed in the longitudinal groove and a clamping strip is inserted in the groove. The clamping shaft is supported in the end walls of the plate cylinder and is movable in locked position by means of worm drives disposed at least at one of the end walls. The clamping shaft has a flattened part on the side receiving the clamping strip and defines a groove, and the latter has a depression on the side receiving the printing plate.

llnited States Patent 1 1 Skiera et al.

[111 3,757,690 1 1 Sept. 11, 1973 1 PRINTING PLATE CLAMPING DEVICE [75] Inventors: Heinz Skiera; llelmut Schumann,

both of Leipzig, Germany [73] Assignee: VEB Polygraph Leipzig, Kombinat Fur Polygraphische Maschinen und Ausrustungen, Leipzig, Germany 22 Filed: Aug. 11, 1971 21 Appl. No.: 170,827

[52] US. Cl. Nil/415.1, 101/378 [51] Int. Cl. B411 27/06 [58] Field of Search 101/4l5.1, 378

[56] References Cited I I v UNITED STATES PATENTS 3,260,200 7/1966 Griinig 101/415.1

3,276,364 10/1966 Langer 101/415.1

FOREIGN PATENTS OR APPLICATIONS 910,627 11/1962 Great Britain 10l/415.1

461 ,540 3/1967 Switzerland 101/4 1 5.1

Primary ExaminerRobert E. Pulfrey Assistant Examiner-Paul T. Sewell Attorney-Ernest G. Montague 5 7 ABSTRACT A printing plate clamping device, particularly for webfed rotary offset printing presses, which comprises a plate cylinder having a longitudinal groove and including end walls. A clamping shaft is disposed in the longitudinal groove and a clamping strip is inserted in the groove. The clamping shaft is supported in the end walls of the plate cylinder and is movable in locked position by means of worm drives disposed at least at one of the end walls. The clamping shaft has a flattened part on the side receiving the clamping strip and defines a groove, and the latter has a depression on the side receiving the printing plate.

4 Claims, 5 Drawing Figures PRINTING PLATE CLAMPING DEVICE The present invention relates to a printing plate clamping device, particularly for web-fed rotary offset printing presses which have a clamping shaft provided in a longitudinal groove in the plate cylinder, by means of which shaft the printing plate is pulled tightly on the one side over the plate cylinder, while the other side is clamped in a hook-like manner at the edge of the longitudinal groove.

Devices of this type have already become known. Among them, the use of two clamping shafts, such as known from German Pat. Nos. 1 165 614 and l 227 480, is, to be sure, avoided. Nevertheless, they are still too expensive in their construction or else they do not assure a correct, exact clamping. Thus, for instance, the clamping device of German Pat. No. 1 087 140 cmploys a clamping ledge around three of the edges on which the printing plate is wrapped, the plate resting on a blunt edge of a side wall of the longitudinal groove of the plate cylinder and acting as a lever, the force arm of which is acted on by a groove of the clamping shaft, while its other arm clamps the printing plate. The side of the printing plate which is to be fastened upon the clamping process is first held fast on the opposite side of the longitudinal groove of the plate cylinder by means of a sharp-edged angle bent on the plate and by means of an eccentric-actuated clamping strip.

The disadvantage of this device resides in particular that the clamping channel, i.e., the zone which cannot be used for the printing, is considerably widened without, on the other hand, any increase in the effective clamping path being obtainable. In addition to the expense for the multiple edging of the printing plates, it was found disadvantageous to tighten the side of the plate which is to be clamped merely in the circumferential direction of the plate cylinder and not pull it into the clamping channel. In this way the peculiarity of plates of forming a bead at the clamping channel cannot be sufficiently counteracted, if at all..

This fact is taken into consideration in the case of the apparatus in accordancewith German Pat. No. l 228- 627, in which there is provided a clamping shaft which has a toothing extending on one part of its periphery over the entire plate region and with which a ledge also provided with toothing cooperates in rack-like manner, as seen in profile. One of the edges of the printing plates must, to be sure, also be provided with an embossed toothing which, upon the insertion of the printing plate, is pushed between the teeth of the clamping shaft and those of the ledge. By turning the clamping shaft, this edge of the plate is then pulled into the clamping channel. The clamping shaft is rotatably supported in the end walls of the plate cylinder and is turned by means of a worm drive.

The expense for the production of the toothed parts and in particular the expense for the impressing of the toothing into each individual printing plate still appears too high in this construction.

It is one object of the present invention, to provide a particularly simple, properly clamping device of multiple possibilities of use and avoiding the aforementioned disadvantages.

It is another object of the present invention to provide a clamping device in which the plate end to be moved is secured by simple means against sliding out of the clamping shaft, and in which at the same time the advantage of the prior art of securing the nonmoved plate end against bending its retained.

It is still another object of the present invention to create a printing plate clamping device which is suitable also for reversible plate cylinders.

In accordance with the present invention, this result is obtained in the manner that the clamping shaft is flattened on the side which receives the clamping ledge and the groove of the clamping shaft on the side receiving the printing plate has a depression, i.e., the groove has a step-shaped bottom.

On the side of the flat portion of the clamping shaft which lies in the direction of clamping, the flat portion is developed as an entry bevel. In accordance with a further feature of the present invention, alongside the supporting points of the clamping shaft on the end sides of the cylinder there are provided lock bridges by means of which the clamping ledge is held in the groove even if no printing plate is inserted and clamped.

In accordance with the present invention, the longitudinal axis of the groove extends between the center axis of the longitudinal groove of the bore of the plate cylinder and the longitudinal axis of the clamping shaft, and that furthermore an entry bevel is provided on both sides of the groove and a depression is arranged on both sides of the bottom of the groove.

The particular advantage of the proposed development of the clamping element resides, on the one hand, in the possibility of practical manufacture, in connection with which the amount of machining can be substantially lowered and, on the other hand, in the fact that the mounting of the plates becomes a simple operation which can rapidly be carried out.

The advantage which the the prior art affords, that upon the clamping of the plate, the side of the printing plate which is first held fast is secured against bending, is furthermore retained in its entirety.

The falling out of the clamping ledge during a rotation of the cylinder without the plate clamped in position is also avoided in a'very simple manner. The printing plate clamping device of the present invention can be used both with plate cylinders intended for one direction of rotation and with reversible plate cylinders, and therefore used in the corresponding printing units for both directions of rotation, without complicated conversion being necessary for the latter, as would otherwise be the case.

With these and other objects in view, which will become apparent in the following detailed description, the present invention, which is shown by example only, will be clearly understood in connection with the accompanying drawings, in which:

FIG. 1 is a fragmentary cross-section of a plate cylinder, in which the clamping device is in a position such as it assumes after the insertion of the printing plate but before the clamping, the printing plate being shown in exaggerated thickness for the sake of clarity;

FIG. 2 is a fragmentary cross-section similar to that of FIG. 1, but with the printing plate clamped in position;

FIG. 3 is also a fragmentary cross-section similar to that of FIG. 1, but at the end of the plate cylinder;

FIG. 4 is a fragmentary cross-section of a reversible plate cylinder, the clamping device'being in a position such as it assumes after the insertion of the printing plate but before the clamping and the clamping of the plate ocurring by a movement of the plate cylinder in the direction indicated by the arrow A;and

FIG. is a fragmentary cross-section similar to that of FIG. 4, but with a previously prepared printing plate clamping which corresponds to the movement of the plate cylinder in the direction indicated by arrow B.

Referring now to the drawings, the plate cylinder 1 has a longitudinal groove 2 which passes into the bore 3. In the latter there is also rotatably arranged a clamping shaft 4, which is supported in particular in the end walls 5 of the plate cylinder 1 and receives in the groove 6 the clamping ledge 7. On this side the clamping shaft 4 is flattened so that, as shown in FIGS. 1 to 3, an edge 8 is formed. The opposite side of the flat portion is developed as an entry bevel 9. As shown in FIGS. 4 and 5, edges 8 and 8 can, however, also be produced by entry bevels 9 and 9', respectively, provided on the two sides of the groove 6. At the bottom of the groove 6 a depression 10 is provided in the case of plate cylinders, which are intended for only one direction of rotation. In the case of reversible plate cylinders, two depressions l0 and 10', respectively, as shown again in FIGS. 4 and 5, are provided through which the printing plate 12 with its edge 12'', which is to be clamped, is introduced up to beyond the actual clamping place at the lower edge of the clamping ledge 7 On each of the end walls 5 of the plate cylinder 1 there is fastened a locking bridge 11, the inner arc 11' of which corresponds to the diameter of the bore 3 and by means of which the clamping strip 7 is held in the groove 6, even if the clamping device is not in operation.

The clamping process takes place as follows:

The forward bent edge 12' of the printing plate 12 is placed over the edge of the clamping channel. After the printing plate has been placed around the plate cylinder, the other edge 12" is inserted into the longitudinal groove 2, and is guided by the entry bevel 9 into the groove 6 and pushed therein until it comes into the depression 10. The clamping shaft 4 is now turned, preferably by hand, until the clamping strip 7 is somewhat oblique with respect to the groove 6 (FIG. 2) and thus via the edge 8 or 8' by the tilting of the strip 7 relative to the groove 6 the clamping strip, secures the printing plate 12 from being pulled out. The clamping is then effected in the known manner, for instance via worm gears (not shown), provided on one or both end sides of the plate cylinder 1.

While we have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense.

We claim:

1. A printing plate clamping device, particularly for web-fed rotary offset printing presses, comprising a plate cylinder having a longitudinal bore therethrough and a longitudinal groove at the surface thereof and communicating with said groove said plate cylinder including end walls,

one clamping shaft disposed in said longitudinal bore,

said clamping shaft being supported in said end walls of said plate cylinder and being rotatable in locked position by means disposed at least at one of said end walls,

said clamping shaft having a flattened part and defining a ledge groove adjacent thereto,

a clamping ledge insertable into said ledge groove and the latter having a width throughout at least substantially equal to the width of said clamping ledge plus the width of an end of said printing plate,

said groove of said clamping shaft having a depression at a bottom of said ledge groove on one side thereof receiving the end of said printing plate, and

said ledge groove having a pivot edge at its top on the other side of said ledge groove and abutting pivotally said clamping ledge so as to press the bottom and opposite side of said clamping ledge against the end of said printing plate clampingly against said one side of said ledge groove, when said clamping ledge is pivoted in said ledge groove.

2. The device, as set forth in claim 1, wherein said flattened part of said clamping shaft forms an entry bevel for said end of said printing plate.

3. The device, as set forth in claim 1, wherein the longitudinal axis of said ledge groove is disposed between a central axis of said longitudinal groove of said plate cylinder and a central longitudinal axis of said clamping shaft,

entry bevels are arranged on said clamping shaft on each side of said ledge groove, and

another depression at said bottom of said ledge groove on the other side of said bottom.

4. The device, as set forth in claim 1, wherein said clamping shaft has supporting points, and locking bridges are provided alongside said supporting points,

holding said clamping in said ledge groove.

l 1! t i 

1. A printing plate clamping device, particularly for web-fed rotary offset printing presses, comprising a plate cylinder having a longitudinal bore therethrough and a longitudinal groove at the surface thereof and communicating with said groove said plate cylinder including end walls, one clamping shaft disposed in said longitudinal bore, said clamping shaft being supported in said end walls of said plate cylinder and being rotatable in locked position by means disposed at least at one of said end walls, said clamping shaft having a flattened part and defining a ledge groove adjacent thereto, a clamping ledge insertable into said ledge groove and the latter having a width throughout at least substantially equal to the width of said clamping ledge plus the width of an end of said printing plate, said groove of said clamping shaft having a depression at a bottom of said ledge groove on one side thereof receiving the end of said printing plate, and said ledge groove having a pivot edge at its top on the other side of said ledge groove and abutting pivotally said clamping ledge so as to press the bottom And opposite side of said clamping ledge against the end of said printing plate clampingly against said one side of said ledge groove, when said clamping ledge is pivoted in said ledge groove.
 2. The device, as set forth in claim 1, wherein said flattened part of said clamping shaft forms an entry bevel for said end of said printing plate.
 3. The device, as set forth in claim 1, wherein the longitudinal axis of said ledge groove is disposed between a central axis of said longitudinal groove of said plate cylinder and a central longitudinal axis of said clamping shaft, entry bevels are arranged on said clamping shaft on each side of said ledge groove, and another depression at said bottom of said ledge groove on the other side of said bottom.
 4. The device, as set forth in claim 1, wherein said clamping shaft has supporting points, and locking bridges are provided alongside said supporting points, holding said clamping in said ledge groove. 